make myChatMessage serializing

app.py

@@ -8,6 +8,12 @@ import gradio as gr
 class myChatMessage(chatglm_cpp.ChatMessage):
     def __deepcopy__(self, memo):
         return chatglm_cpp.ChatMessage(self.role, self.content)
+    def __getstate__(self):
+        """Used for serializing instances"""
+        return (self.role, self.content)
+    def __setstate__(self, state):
+        """Used for deserializing"""
+        self.role, self.content = state
 
 init_history = [
     myChatMessage(role="user", content='你讀過《故事課》嗎？'),